The present invention relates to a seatbelt retractor to be installed in a vehicle such as an automobile or the like for retracting a seatbelt with a motor to restrain and protect a passenger and, more specifically, relates to a seatbelt retractor including a clutch mechanism for efficiently retracting a seatbelt with small power consumption. The present invention also relates to a seatbelt device provided with the seatbelt retractor.
Conventionally, a seatbelt device is installed in a vehicle such as an automobile or the like, and in case of emergency when great deceleration acts upon a vehicle in a collision or the like, a seatbelt restrains a passenger so as to prevent the passenger from being thrown out of the seat, thereby protecting the passenger. Such a seatbelt device includes a seatbelt retractor for retracting the seatbelt. The seatbelt retractor includes forcing means such as a spiral spring or the like for forcing a spool to rotate in a belt-retracting direction all the times for winding the seatbelt thereon. That is, the seatbelt is wound onto the spool due to the force of the forcing means when the passenger does not wear the seatbelt.
On the other hand, the seatbelt is extracted against the force of the forcing means when the passenger wears the seatbelt. The seatbelt retractor has lock means for prohibiting rotation of the spool in a belt-extracting direction in case of emergency such as the aforementioned examples, thereby prohibiting extraction of the seatbelt in case of emergency. Thus, with the seatbelt, the passenger is restrained and protected in a sure manner in case of emergency.
In such a conventional seatbelt device, a generally constant belt tension is applied to the seatbelt with the forcing means at the time of wearing the seatbelt. Accordingly, the seatbelt retractor operates generally in a single mode regardless of a situation of the vehicle including the seatbelt device and the surroundings thereof. In this case, while the conventional seatbelt device restrains and protects the passenger in a sure manner in case of emergency as described above, the seatbelt is not controlled so as to provide comfortable wearing for the passenger in situations other than emergency. Furthermore, there is increased demand for a seatbelt wherein the passenger is more stably restrained so as to be protected in a surer manner in case of emergency.
Japanese Patent Publication (Kokai) No. 2002-104135 has disclosed a passenger restraining/protecting system in which a motor is provided for controlling rotation of the spool of the seatbelt retractor corresponding to a situation of the vehicle including the seatbelt device and the surroundings thereof so as to adjust belt tension, thereby more efficiently restraining and protecting the passenger, and providing more comfortable wearing for the passenger.
In the seatbelt retractor disclosed in Japanese Patent Publication (Kokai) No. 2002-104135, when the motor is not driven, a power transmission path for transmitting the driving force of the motor to the spool is disconnected so that the driving force is not transmitted to the spool, and both the motor and the spool rotate freely. When the motor is driven in the belt-retracting direction (referred to as forward rotational direction) for retracting the seatbelt, the power transmission path is connected through the forward rotation of the motor, thereby transmitting the driving force of the motor to the spool. Accordingly, the seatbelt retractor is controlled so that the spool rotates in the belt-retracting direction so as to retract the seatbelt by the driving force of the motor, thereby increasing the belt tension. Furthermore, in this case, when the motor rotates in the reverse direction for releasing the seatbelt, the power transmission path is disconnected. As a result, both the motor and the spool rotate freely, i.e., the spool is not affected by the driving force of the motor.
As described above, in the seatbelt retractor disclosed in Japanese Patent Publication (Kokai) No. 2002-104135, when the motor rotates, the clutch for controlling the power transmission path is connected so as to connect the power transmission path. On the other hand, when the motor rotates in reverse, the clutch is disconnected so as to shut off the power transmission path.
In the seatbelt retractor disclosed in Japanese Patent Publication (Kokai) No. 2002-104135, it is necessary to stop the motor after the power transmission path is disconnected and the clutch of the power transmission path turns off. Accordingly, in a conventional seatbelt retractor, a period of time for reverse rotation is set based on a period of time from the start of the reverse rotation of the motor to completion of disconnecting the clutch. In this case, the period of time required for disconnecting the clutch varies according to an operating situation of the retractor. Accordingly, the period of time for the reverse rotation is set to be a maximum period of time required for disconnecting the clutch in every situation. As a result, in every situation, the motor stops driving after completion of disconnecting the clutch in a sure manner.
However, when a fixed period of time for the reverse rotation of the motor for disconnecting the clutch is set, the motor rotates in reverse for a relatively long time in most ordinary situations, thereby always generating mechanical noise. While the mechanical noise causes no particular problem in the seatbelt retractor disclosed in Japanese Patent Publication (Kokai) No. 2002-104135, the mechanical noise is preferably suppressed as much as possible.
In view of the problems described above, the present invention has been made, and an object of the invention is to provide a seatbelt retractor having a configuration wherein power consumption of the motor is reduced and a mechanical noise is suppressed when the clutch is disconnected.
Another object of the invention is to provide a seatbelt device provided with the seatbelt retractor.
Further objects and advantages of the invention will be apparent from the following description of the invention.